A liquid crystal panel is used as a display of computers or televisions. A glass substrate for liquid crystal displays (hereinafter, referred to as an LCD substrate) has been enlarged increasingly in recent years. Various semiconductor manufacturing processes are performed for forming devices such as a thin film transistor (TFT) on the LCD substrate. Among such processes, a heat treatment process is performed by a single-wafer type cold-wall heat treatment apparatus, which processes substrates one by one. This apparatus heats a substrate carried in a chamber from above by a heating lamp. As for a large-size LCD substrate, since heat radiation from a circumferential edge is large, it is preferable to use a hot-wall type heat treatment apparatus which heats a substrate while heating walls of a reaction container by a heater surrounding the reaction container.
Meanwhile, recently, in order to achieve a higher throughput, a system referred to as a cluster tool is used, which is constituted by connecting airtightly a carrier chamber, which performs carry-in and carry-out of a substrate carrier, to a conveyance chamber in which a convey arm is installed and further connecting airtightly a plurality of heat treatment chambers to the conveyance chamber.
The hot-wall type heat treatment apparatus requires a long time for heating and cooling a substrate. For example, when a substrate is attracted onto a placement stage by an electrostatic chuck as in a cold-wall type heat treatment apparatus, a rapid heat exchange can be performed between the substrate and the placement stage by supplying a heating medium to an extremely small gap between the backside of the substrate and the placement stage. However, since the electrostatic chuck cannot be used in the hot-wall type, a large gap is present between a substrate and a placement stage. For this reason, if an attempt is made to take measures of a cold-wall type, especially in a case of a large-size LCD substrate, it is difficult to cool down uniformly and rapidly. Therefore, when an attempt is made to incorporate a hot-wall type heat treatment apparatus which performs a heat treatment of an LCD substrate, it takes a long time to heat and cool the substrate by the heat treatment apparatus, and, thus, there is a problem in that a function of a high throughput which is provided by a cluster tool cannot be sufficiently used.